The present application claims priority to Japanese Application No. P10-229101 filed Aug. 13, 1998 which application is incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
The present invention concerns a method of manufacturing a nitride series III-V group compound semiconductor with improved crystallinity by controlling a flow rate ratio between a starting material gas and a carrier gas.
2. Description of the Related Art
In recent years, a demand for higher density and higher resolution has been increased with regard to recording and reproduction, for example, to optical disks and magneto-optic disks, and development has been made for semiconductor lasers emitting green beam and blue beam in order to shorten the wavelength of a laser beam irradiated to the recording media.
As a material used for manufacturing a semiconductor device capable of emitting a laser beam at a short wavelength, it has been known that nitride series III-V group compound semiconductors such as GaN, AlGaN and GaInN are suitable (for example, Jpn. J. Appl. Phys. 30 (1991) L1998).
In the growing, for example, epitaxial growing, of a nitride series III-V group compound semiconductor, an organic metal gas phase growing method (MOCVD method) capable of controlling the supply of starting material accurately and with reproducibility is suitable.
Further, when the growing of the nitride series III-V group compound semiconductor is conducted by the organic metal gas phase growing method, ammonia can be applied as the starting material for the group V, namely, as the nitrogen starting material.
Ammonia is a relatively thermally stable material and gas phase growing of the nitride series III-V group compound semiconductor using the same as the starting material is conducted at a temperature of 1000 to 1200xc2x0 C.
Further, since the decomposing efficiency of ammonia is relatively starting and nitrogen starting material species formed after decomposition of ammonia have high vapor pressure, a great amount of ammonia has to be supplied upon growing the nitride series III-V group compound semiconductor using ammonia as the starting material, and the molar ratio of the group V starting material to the group III starting material such as trimethyl gallium (TMGa), trimethyl aluminum (TMAl), trimethyl indium (TMIn) and the like, namely, the group V starting material (mol)/group III starting material (mol) is as high as about 1000 to tens of thousands.
With the situations as described above, an ammonia gas is supplied in an amount as large as possible in a case of growing the nitride series III-V group compound semiconductor.
However, no sufficient studies have been made in the prior art for improving the crystallinity of a compound semiconductor by controlling the ratio of the ammonia gas to be supplied and gases other than ammonia such as a hydrogen gas supplied together. Accordingly, many non-light emission centers are incorporated in the crystals of the thus manufactured semiconductor compound, and it has been desired to improve the crystallinity of the semiconductor compound.
In view of the above, the present invention provides a method of manufacturing a nitride series III-V group compound semiconductor with an aim of obtaining crystals of excellent light emitting properties in a case of manufacturing the nitride series III-V group compound semiconductor by gas phase growing using a starting material for the group III element, ammonia as starting material for group V element and hydrogen, by controlling the gas phase molar ratio of hydrogen to the total amount of hydrogen and ammonia (H2/(H2+NH3)) thereby reducing the number of non-light emission centers incorporated in the crystals.
In the manufacture of a nitride series III-V group compound semiconductor by a gas phase growing using a starting material for a group III element, ammonia as a starting material for a group V element and hydrogen, a method of manufacturing a nitride series III-V group compound semiconductor according to the present invention is conducted by specifying a range of a gas phase molar ratio of hydrogen to the total amount of hydrogen and ammonia (H2/(H2+NH3)) within a predetermined range.
The method of manufacturing the nitride series III-V group compound semiconductor according to the present invention is conducted by specifying a range of the gas phase molar ratio of hydrogen to the total amount of hydrogen and ammonia as the starting material for the group V element in the starting gas suitable to the manufacture of the compound semiconductor of excellent crystallinity to 0.3 less than (H2/(H2+NH3)) less than 0.7, 0.3 less than (H2/(H2+NH3)) less than 0.6 or 0.4 less than (H2/(H2+NH3)) less than 0.5.